Assuming you have a 1971 land barge from your name. The 1971 through 1976 models where the largest and the heaviest B-bodies built. With a curb weight of 4,330 pounds empty (but does include oil in pan and five gallons of gas, not found on the shipping weight). That is a lot of mass to accelerate, even with a 7.0 liter LS (though yours could be as small as a 4.3L).
As to who makes adjustable control arms I would look to Hotchkiss. If you are serious about draging it you will eventually need to reinforce the upper control arm mounting points as they are in tension on launch, and with a lot of flogging they will pull loose.
On my 1985 Impala (the ninth and final version of the B-body) I got my weight down to 3,280 pounds by putting the car on a very strict diet. Dropped in a thousand horsepower BBC under the hood and on a properly prepped track while running 12 inch wide slicks I could stand it on it's back bumper while clicking of a 9.39 in what was essentially an old taxi cab.
I used to drive it on the street all the time, but traction was nearly impossible, just smoking the tires for two or three blocks was the best I could do without wide tires and a lot of rubber cement.
Hotchkis has some really nice adjustable upper control arms for the rear-end if you stay with the stockish design. You may want a rear sway bar as well, I got one from Addco. (resold through many places)
I *think* that the RideTech guys (Air Ride) have a coil-over kit for the rear if you got more $$ to go that way.
PS. I got this video across my Facebook the other day. Pretty badass. You could jump straight to the 1:00m mark.....
I used aftermarket tubular control arms with a Dana 60 sporting 35 spline axles and a Detroit Locker. With something this heavy a locker beats a limited slip rear end; and it offers the possibility of driving on the street which you can not do that with a spool, even though a spool allows you to run 45 spline axles. A spool will break even a 45 spline axle when trying to turn.
A Detroit Locker differs from a PosiTraction limited slip in that a locker is just that locked all the time unless the pressure of turning forces it apart to allow one axle to turn faster than the other. Positraction is always open and when not turning both axles are forced to rotate at the same speed by spring pressure and the number of clutch discs in the differential. The Eaton Posi allows you to modify the number of clutch discs by taking out the stock ones and inserting thinner steels and clutches in there place. Eaton also offers three different spring pressures for the rear. 400 psi is stock spring pressure which can be doubled to 800 pounds of pressure for drag racing, or halved to only 200 pounds for road racing. Both the "Posi" and the Detroit Locker are made by Eaton: that also makes the TrueTrac (great for BMW and Porsche and many road racers love them in their race cars, but is torque limited). Eaton makes three other differentials that are not as popular because they are not as strong as the first two I mentioned.
Moser offers a modified 12 bolt Eaton Posi that will accept a 31 spline axle in a 12 bolt rear so the only difference between the 12 bolt and the Ford designed "Nine Inch" that no one uses (they haven't been made since 1986 and they are no stronger than Spicer 10 bolt in stock trim as they have only 28 spline axles). Since both the 12 bolt and the aftermarket Nickel case nine inch are equally strong why would you install a rear end that eats one and a half to two percent of your flywheel horsepower to turn it due to added friction, and has issues with the housing if not reinforced.
The Spicer 12 bolt is a modified Dana 44 (the 10 bolt is a Dana 30). With Dana the bigger the number the stronger the rear end. However under NHRA rules you can not use a truck rear end under a car. Since I source my Dana 60's out of Ford F350 trucks one asks how cam I do this. Thank Chrysler. Chrysler used a Dana 60 behind their 426 Hemi headed 'cudas (E body cars) and the 440 powered B-body vehicles (Super Bee, GTX, and the Road Runner). Thus my Dana 60 is in fact a car rear end even if I source mine from a truck.
You need to have double adjustable shocks (I used coil overs) and you need at a minimum polyurethane bushings every were you find rubber. For a dedicated drag car I recommend Aluminum bushings or steel Hiem joint (required if you use a triangulated four link as found on the 1971 through 1999 B-body). You can use the Anti Roll bar (aftermarket frame mounted) to preload your suspension (if you don't have an aftermarket adjustable anti roll bar you will need an air bag on the passenger side. Pinion angle is important to prevent breaking your 1410 universal joints. You want to reduce the angle to reduce friction but not to be straight. You get body separation to plant the tire by adjusting the shocks.
BA. I’ve tried to find away to get ahold of MR.Grace and ask him about his set up. His red 66 is why I got my 66. My last car was a 78 Malibu that ran [email protected] G body there 100’s of drag racing parts to set up a car. Impala’s are being hard to find such parts...lol
The rear suspension on the B bodies are fairly simple and without going into back halfing the car the best your going to be able to do is swap out stock parts for adjustable and stronger parts. Then adding some reinforcement. If I had the perimeter frame with a primary duty of drag racing I would definitely go the back half route. Unfortunately I have X frame cars so when you start talking back half you end up replacing 2/3rds or more of the frame to make it work, not that it isn't still being thought of as a long term plan on my more door. A lot depends on after I get it road worthy will it be more of a cruiser or a Saturday night special.
I used to drag race Camaros but discovered that the Nova was a better choice asa drag car because it cost less (No one wanted it when given a choice of a Camaro), it used Camaro parts so it was the same as a Camaro in handling and The best part it had more head room for some one who stands six foot six.
Down side to a F-Body (Camaro) or an X-body (Nova) is that it only has a front sub frame. The rest of the car is just a sheet metal shell that flexes under stress. So you have to back half the car which requires frame connectors to get a full frame. Back having isn't expensive (may be $790 to $1,200 depending upon suspension choices). It does allow flexability in setting up the car up for drag racing, or road racing or just the street (those kits are around $500). You can buy a full frame for the Nova for about $2,400 which adds strength while reducing weight.
The B-Body has a full frame or at least a good start towards one. You need to fully box the frame (the deeper convertible frame is boxed only under the doors but it also adds an extra cross-member to add a rung to the ladder) front to back to add stiffness.
As I have mentioned in previous posts if you are going drag racing with a lot of torque you also need to reinforce the mounting points on the sheet metal where the suspension mounts. I cut off the old and used it as a template to make a five hole mounting point top- and bottom car side for an adjustable four link using a Panhard bar to center it (my car had triangulated four control arms that were too flimsy and offered no change to the pinion angle). I went with a parallel tube linkage with shocks mounted behind the axle and a Dana 60 differential that didn't have the eye holes to use the factory triangulated control arms (Strange Engineering makes a triangulated D60 that has those ears with mounting holes if you want to go that route).
All drag races are won or lost in the first sixty feet. The days of running down your competitor on the top end doesn't exist in today's heads up competition. Because of fine tuning of the NHRA class rules every one has about the same power level to weight in the top ranks. So suspension is just as important as is engine building. Because of this it is no longer fun but more of a business with no profit incentive. If you want fun race a station wagon with a 283 or a small six in a Chevy II in the bottom of the class ranks. There winning and loosing is luck and driving skills.
I've been running the same 12 bolt with Strange axles (c-clip eliminators) and spool for about 15 years. It's driven on the street more than the track, but was neglected the past few year while I was working on a different project. Sounds like it really depends on where & how it's driven. I'm back here today for some long needed TLC . Stay Safe